Heat exchanger, boiler, and the like



A. T. HERP EN HEAT EXCHANGER, BOILER AND THE LIKE Filed Feb. 12, 1932Aug. 20, 1935.

. ,bNvENToR A0005 2- 771F000? HERPEN.

I B-Y ATTORN EYS atented Aug. G, W

HEAT EXCHANGER, BOILER, AND THE LIKE August Theodor Herpen, Berlin,Germany, assignor to La Mont Corporation, New York, N. Y.

Application February 12, 1932, Serial No. 5925501 In Germany February13, 1931 8 Claims. (Cl. 122-235) This invention relates to steamgenerators and especially to steam generators having a positivecirculation of water therein. More particularly the invention relates tosteam generators in which the heating surface is in the form of tubeswhich are subjected to radiant heat and to the heat of heating gases.

In steam generators with positive water circulation it is necessary todistribute the circulated water to the individual heating surfaces inaccordance with the transfer of heat. Whereas in a steam generator withnatural convection circulation an increased rate of steam generationcauses a stronger circulation of the water over the heating surfacesexposed to higher heat as compared to those exposed to less heat, in asteam generator with positive water circulation the reverse may be true.the heating surface subjected to higher heat a greater amount of steamis generated and this steam flowing through tubes or over heatingsurfaces creates a higher resistance to circulation of the water.Therefore, in a group of heating surfaces arranged in parallel, for agiven total quantity of water circulated, the water delivered to theheating surfaces exposed to higher heat will be less in proportion tothe amount of steam generated therein than that delivered to the heatingsurfaces exposed to less heat because the resistance of the latterheating surfaces is correspondingly less. The pressure which producesflow of the water in the so-called convection circulation is the resultof the steam generation within the tube or upon the heating surfacewhereas in a steam generatqr in which the water is positively deliveredby means such as a pump, the pressure is applied at the ends of thetubes or at the entrance to the heating surface. Ina system of paralleltubes or paths of water flow, if the: same pressure is applied by thepump at the entrance to all the tubes or paths, a greater amount ofwater will flow into the tubes subjected to less heat than into thosesubjected to great or heat. The reason for thisis that the smalleramount of steam generated in the tubes sub- That is to say, upon withrespect to the water flow, as is usually the case. The relativeabsorption of heat by heating surface under radiant heat as comparedwith the absorption by the convection heating surface changes with theload. As is well known the relative heat absorption of the heatingsurface under radiant heat decreases with the load of the boiler,whereas the relative heat absorption of the convection heating surfaceincreases with the load. An unbalance or lack of equalization thereit)According to the present invention tubes ar- 15 ranged in parallel andhaving positive water circulation are positioned so that they arejuxtaposed approximately in a bank forming a heating surface subjectedto radiant heat, as when the tubes are located at the wall or roof of afurnace 2o chamber. The same tubes are extended beyond the radiant heatzone and are bent upon themselves, for example in serpentine form toprovide a group of heating surfaces subjected to the heat of the gasesfor generating steam by convection 5 heating. The water is thus causedto flow in separate paths consecutively through the zones of radiant andconvection heat.

One advantage of the invention consists in the fact that on account ofthe series arrangement 30 of radiation and convection heating surfacesthe sum of the heat absorbed by the parts, such as the tubes, throughwhich the water separately flows, under changing load. on the boilermaintains approximately a constant relation to the total heat 35absorption of the boiler and therefore a better distribution of thewater to be circulated can be obtained. Moreover the invention providesthe advantage that as the tubes are continuous and of long length toextend through both zones the 40 number of the connection points, as toa header, is decreased and because of the larger total heat absorptionand correspondingly larger steam pro- 'duction of each tube, thevelocity of the mixture of steam and water in the tubes is increasedwhich assists in increasing the heat transfer.

The invention also makes it possible to obtain the same advantage in asuperheater having surfaces over which the steam being superheated flowsin series over portions subjected to radiant 56 heat and to convectionheat. Here also the sum of heat absorption remains approximatelyconstant for changing loads. The heat absorption of the superheater as awhole can be made proportional. to the heat absorption of the steamgenerator at all loads by intersperslng the superheater tubes betweenthe steam generating tubes in the radiation part of the boiler and byarranging the same steam generator and superheater tubes by bending thetubes one or more times so as to form a group of steam generating andsuperheating surfaces traversed by the heating gases.' In such anarrangement depending upon the number of superheater tubes interspersedbetween the steam generating tubes the heat absorbed by the superheaterwill bear a certain relationto the heatabsorbed by the steam generator,so that the temperature of superheated steam will besubstantiallyconstant at all loads.

It is of particular advantage to have the steam flow in the superheaterin a counter-flow relation to the heating gases not only in theconvection steam generator but also at the radiation heating surface.

The invention also has the further advantage that because of theinterspersed arrangement of the superheater tubes and the steamgenerating tubes the superheater tubes are protected against burningout.

In the drawing a typical embodiment of the in vention is shown, but theinvention of course is not limited to this particular embodiment.

Fig. 1 shows acombination of steam generating tubes according to theinvention with superheating tubes similarly arranged; and

Fig. 2 is a cross section upon line 22 of Fig. 1.

Fig; 1 illustrates-a longitudinal section and Fig. 2 a cross section ofa steam generator with a radiant heat and a convection heat superheater.The roof of the combustion chamber is lined with tubes placed side byside in relatively close spacing. Some of these tubes are used forgenerating steam and others are used for superheating the steam. Thetubes are long enough to be bent into U or serpentine shape to form, inthe gas passage leading from the furnace, the convection heating surface26 in which the tubes are separated somewhat to permit passage of thegases thereover. In Fig. 1 the steam generating tubes are shown at I6and superheater tubes at IT. The water is positively delivered by meanssuch as the pump 2| and is fed through the tubes from distributingheader I. The mixture of water and steam formed in the generation ofsteam is introduced into the drum 3, where the steam is separated fromthe water. The steam flows from the drum 3. through the superheatertubes I I in counterflow relation to the heating gases. It also flowsalong the radiation surface in a direction, toward the collector I8which is adjacent the header I. From the header I8 the steam may bepassed to -the place of use. The heating gases passing through the groupof heating surfaces formed by the steam generating tubes and superheatertubes may be delivered to the feed water preheater I9 for furthercooling. An air preheater 20 also may be used if desired.

It is of advantage to connect the superheater tubes immediately to thesteam space of the drum because thereby a practical simplification ofthe construction is obtained. Also by this means the steam may be takenoff over the full length of the drum 3. The steam is thus discharged atmany points just as the mixture of steam and water from the steamgenerating tubes I6 is introduced into the drum 3 at many points. Duringstartthem by means of the circulation pump 2| (Fig. I) which is used toproduce circulation of the water through the steam generating tubes ofthe steam generator. Water from the drum 3 flows to the pump 2I throughthe pipe 22. The pump during normal operation forces the water throughthe pipe 23 into the water distributor I. If no steam flows through thesuperheater tubes the valve 24 may be opened and water is forced throughthe collector I8 and the superheater tubes I1. The superheater surfacein this event acts as a steam generator, whereby a reliable cooling issecured.

What I claim is:-=-

1. Steam generator comprising a furnace, a plurality of tubes exposed tothe radiant heat of said furnace and extending beyond the furnace inspaced relation to form a tube bundle for absorption by convection ofthe heat of the heating gases discharged from the furnace, a steamsuperheating tube in interspersed relation to the portions of the tubesexposed to radiant heat for superheating the steam by radiant heat, saidsteam superheating tube also extending in interspersed relation withsaid tube bundle to'receive I heat from the gases by convection.

superheating the steam by radiant heat said steam superheating tube alsoextending in interspersed relation with said tube bundle -to re-' ceiveheat from the gases by convection, said steam generating tubes beingconnected to a drum to discharge steam thereto, said steam superheatingtube being also connected to said drum to receive steam therefrom.

3. Steam generator comprising a furnace, a plurality of tubes exposed tothe radiant heat of said furnace and extending beyond the furnace inspaced relation to form a tube bundle for absorption by convection ofthe heat of the heating gases discharged from the furnace, a steamsuperheating tube in interspersed relation to the portions of the tubesexposed to radiant heat for superheating the steam by radiant heat, saidsteam superheating tube also extending in interspersed relation withsaid tube bundle to receive heat from the gases by convection, saidsteam generating tubes having water delivered to one end thereof anddischarging steam from the other end thereof, said steam superheatingtube being arranged to receive adjacent the discharge ends of the steamgenerating tubes the steam discharged from said steam generating tubesand being arranged to discharge the superheated steam at the end of saidsteam superheating tube remote from said discharge ends of said steamgenerating tubes.

4. Steam generator comprising a furnace having a wall, a gas passageconnected to receive the combustion gases from said furnace, a pluralityof tubes extending along said wall and into said gas passage,theportions of said tubes in said gas passage being bent to positionportions of the lengths thereof in spaced relation to each other forabsorption of the heat of the gases passing from said furnace throughsaid gas passage, some of said tubes being connected at one end thereofto receive water from a common water header and being arranged todischarge. from the other end thereof the generated steam and any waterflowing to said discharge end with the steam, others of said tubes forsuperheating steam being connected to a common steam discharge headerand arranged to receive steam for flow through,

said steam superheating tubes toward said dis-.

I charge header, whereby said steam being superheated receivessuccessively in eachtube heatboth by radiation and convection heattransfer in similar relation to the heat absorbed by the steamgenerating tubes.

.' 5.'Steam generator comprising a furnace having a wall, a gas passageconnected to receive the thereof to receive water from a common waterheader and being arranged to discharge from the other end thereof thegenerated steam and-any water flowing to said discharge end with thenected to a common steam discharge header at the ends-of said steamsuperheating tubes remote from the steam discharge end of the steamgencrating tubes, whiareby the steam generated in said steam generatingtubes is superheated in said superheating tubes first by convectionaction in counter-flow relation to the heating gases and.

then by the radiant heat of the furnace.

' 6. Heat exchanger comprising a plurality of fluid confining tubesincluding steam superheating tubes and steam generating tubes, saidfluid confining tubes extending in the same general direction in a zoneof radiant heat; said tubes having a'portion of their-lengths extendingout of said radiant heat zone and into a passage through which heatinggases flow, said portions within said gas passage being in spacedrelation for the flow of gases therebetween and being bent into aplurality of coils to form a bundle of tubes arranged to receive heatfromsaid gases by convection, said tubes each providing a single path offluid flow consecutively through said zones, said steam superheatingtubes having the portions thereof exposed to radiant heat interspersedwith the portions of the steam generating tubes exposed to radiant heat.

7. Heat exchanger comprising a plurality of fluid confining tubesincluding steam superheating tubes and steam generating tubes, saidfluid confining tubes extending in the same general direction in a zoneof radiant heat, said tubes having a portion of their lengths extendingout of said radiant heat zone and into a passage through which heatinggases flow, said portions within said gas passage being inspacedrelation for the flow of gases therebetween and being bent into aplurality of coils to form a bundle of tubes arranged to receive heatfrom said gases by convection, said tubes each providing a single pathof fluid flow consecutively through said zones, said steam superheatingtubes having the portions thereof exposed to radiant heat interspersedwith the portions of the steam generating tubes exposed to radiant heat,said superheater tubes being so arranged in the gaspassage with respectto their inlet ends-that the steam flows through said tubes in counterflow relation to the heating gases.

8. Heat exchanger comprising a plurality of fluid confining'tubesincluding steam superheating tubes and steam generating tubes, saidfluid confining tubes extending in the same general direction in a zoneof radiant heat, said tubes having a portion oftheir lengths extendingout of said radiant heat zone and into a passage through which heatinggases flow, said portions within said gas passage being in spacedrelation for theflow of gases therebetween and being bent into aplurality of coils to form a bundle of tubes arranged to receive heatfrom said gases by convection, said.tubes each providinga single'path offluid flow consecutively through said zones, said steam superheatingtubes having at least a portion of their lengths interspersed with thesteam generating tubes, said interspersed portions being selected forboth types of tubes from those portiens thereof which are exposed toradiant heat and to convection heat.

AUGUST THEODOR HERPEN.

